Linear actuators are devices that produce linear motion, usually in response to a rotary input. Advances in various areas of technology have created a need for actuators of increased accuracy. One area of particularly critical need relates to the positioning of lenses and mirrors used with lasers Another exemplary area is the growing of semiconductor crystals which require a precise rate of movement. A further example is high accuracy micrometers.
Many known linear actuators that are intended to be highly accurate operate on the principle of a conventional micrometer in which a spindle is threadedly received within a sleeve. The accuracy of such a device is largely dependent upon the tolerance of the threads. What is commonly referred to as a standard micrometer thread will provide linear movement with an accuracy of about 0.0001 at best. Efforts to improve this accuracy by more precise machining of the threads typically produce only a marginal gain in accuracy at substantially increased cost.
Another known approach to improving the accuracy of a linear actuator is the use of an electronic "location sensor" which detects the location of the moving actuator element and provides a feedback signal by which the position of that element is adjusted. These electronic devices not only add considerable cost and complexity, but are inherently limited by the accuracy of the sensors themselves, which is often inadequate.
An objective of the present invention is to provide a relatively simple mechanical linear actuator that can be manufactured at a reasonable cost but has very significantly improved accuracy.